Download - Conclusion of the experiment in canada!
Growth of ZnO ZnSe nanowires
Yuya Sakamoto
Character of ZnO ZnSe Nanowire (NW)
WZ ZnOZB ZnSe
2.8 eV3.2 eV
1.9 eV
Feature
・ Type-II heterojunction・ ZnSe and ZnO have a wide bandgap・ Lattice mismatched combinations
WZ ZnOWZ ZnSe
2.8 eV
3.2 eV1.5 eV
For Photovoltaic devices
Increase surface-to-volume-ratio
Chemical Vapor Deposition (CVD) method
Quartz tube heaterAu on Si substrate ZnO/C or ZnSe
Ar Gas inletAr Gas outlet
0 10 20 30 40 50 600
400
800
1200
Position [cm]
Tem
pera
ture
[]
℃
Two-step CVD method
Au
Si ZnO
Si
First step Second step
ZnSeSi
ZnSe
Si
ZnOSi
ZnO/ZnSe Core/Shell NW
ZnO ZnSe Branch NWSi
Growth conditions of ZnO/ZnSe core/shell NWs
Au
Si
ZnO
Si
ZnSe
Si
Temperature Duration Ar gas flow rateFirst step 600 60 min 125sccm
Second step 590 60 min 235sccm
Source material : ZnO (99.99%) and C(99.9%) with the weight ratio of 1:1 : ZnSe (99.99%)Thickness of Au film : 10 nm
SEM imageZnO NWs ZnO/ZnSe core/ shell NWs
The average NW diameter : 40 nm → 75 nm
500 nm 500 nm
1 μm 2 μm
EDX spectrum
The diameter correspond to ZnO/ZnSe core/shell NW
0 20 40 60 80 100 120 140 160 180 2000
50100150200250300
Distance [nm]
Inte
nsity
[a. u
.]
1 μm
90 nm120 nm
Photoluminescence Spectrum
ZnO Bandedge (BE) emission : 380 nm = 3.26 eVZnSe BE emission : 460 nm = 2.69 eV
ZnSe Deep Level (DL) emission: 640 nm = 1.93 eV
Laser wavelength : 361.2 nmRoom temperature
Growth conditions of ZnO ZnSe branch NWs
Au
Si
Temperatu Duration Ar gas flow rateFirst step 640 60 min 235sccm
Second step 590 60 min 125sccm
ZnSe
SiZnO
Si
Source material : ZnO (99.99%) and C(99.9%) with the weight ratio of 1:1 ZnSe (99.99%)Thickness of Au film : 10 nm
SEM imageZnSe NWs ZnO ZnSe branch NWs
The average diameter of thin NWs is 29 nm → 33 nm
5 μm 5 μm
1 μm 1 μm
0 50 100 150 200 250 3000
100200300400
Distance [nm]
Inte
nsity
[a. u
.]0 30 60 90 120 150 180
050
100150200
Distance [nm]In
tens
ity [a
. u.]
ZnO ZnSe branch NW data by EDX line profile
2
1 1
2
1 μm
PL
ZnSe BE emission : 442 nm = 2.8 eV
ZnSe DL emission : 640 nm = 1.9 eVZnO BE emission : 380 nm =3.26 eV
Laser wavelength : 361.2 nmRoom temperature
Conclusion
・ Characterize the ZnO/ZnSe core/shell NWs and ZnO ZnSe branch NW by XRD and PL
・ Observe the surface morphology of ZnO/ZnSe core/shell NW, and ZnO ZnSe branch heterostructure NW by SEM
・ Found the conditions for growth ZnO/ZnSe core/shell heterostructure NW, and ZnO ZnSe branch heterostructure NW
Future Work
・ Measure the electrical property by Electron beam induced current
・ Fabricate the single NW device with ZnO ZnSe branch structure NW by electron beam lithography
・ Upgrade the quality of ZnO and ZnSe NWs before growth second material
・ Measure the junction of ZnO and ZnSe by transmission electron microscopy to confirm ZnO NWs are connecting to ZnSe NWs
Acknowledgement
・ I would like to express my deep gratitude to Professor Harry E. Ruda, for his patient guidance and useful critiques of this research work.
・ I would also like to thank Dr. Carlos Fernandes, for his advice and assistance in keeping my progress on schedule.
・ I would also like to thank Dr Souza Christina and Dave Wisnieski for measuring PL spectrum and teaching me how to analyze spectrum.
・ I wish to express my sincere gratitude to all of the concerned people, who help me to finish my all procedure, correct my English, promote my experiments.
Laser reference
330 360 390
0
2000
4000
6000
Inte
nsity
(arb
.uni
t)
Wavelength (nm)
Leaser reference
Analysis
The mean diameter of base : 223 nm
The mean diameter of branch : 52 nm
The diameter of ZnO was also almost 40 nm
ZnSe : June 28
ZnO : July 4
ZnO ZnSe branch NW data by EDX line profile
①
②
②
①
There is the ZnSe ZnO hetero structure NW
My opinion
I measured 20 NWs by ESM and EDX. The compositions of thin NWs were ZnSe
ZnO NWs weren’t grown on ZnSe NWs
ZnO
Au
ZnSe
Before using EDX,I guessed this structure
ZnO
ZnSe
After using EDX, I believe it was happened in the furnace
∆𝐸𝑉+∆𝐸𝑣=¿